package demos;

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

public class ComboBoxDemo extends JPanel implements ActionListener
{
  private static final long serialVersionUID = 7691860869035378862L;
  JLabel picture;

  public ComboBoxDemo()
  {
    super(new BorderLayout());

    String[] petStrings = {"Bird", "Cat", "Dog", "Rabbit", "Pig"};

    // Create the combo box, select the item at index 4.
    // Indices start at 0, so 4 specifies the pig.
    JComboBox petList = new JComboBox(petStrings);
    petList.setSelectedIndex(4);
    petList.addActionListener(this);

    // Set up the picture.
    picture = new JLabel();
    picture.setFont(picture.getFont().deriveFont(Font.ITALIC));
    picture.setHorizontalAlignment(JLabel.CENTER);
    updateLabel(petStrings[petList.getSelectedIndex()]);
    picture.setBorder(BorderFactory.createEmptyBorder(10, 0, 0, 0));

    // The preferred size is hard-coded to be the width of the
    // widest image and the height of the tallest image + the border.
    // A real program would compute this.
    picture.setPreferredSize(new Dimension(177, 122 + 10));

    // Lay out the demo.
    add(petList, BorderLayout.PAGE_START);
    add(picture, BorderLayout.PAGE_END);
    setBorder(BorderFactory.createEmptyBorder(20, 20, 20, 20));
  }

  /** Listens to the combo box. */
  public void actionPerformed(ActionEvent e)
  {
    JComboBox cb = (JComboBox) e.getSource();
    String petName = (String) cb.getSelectedItem();
    updateLabel(petName);
  }

  protected void updateLabel(String name)
  {
    ImageIcon icon = createImageIcon("images/" + name + ".gif");
    picture.setIcon(icon);
    picture.setToolTipText("A drawing of a " + name.toLowerCase());
    if(icon != null)
    {
      picture.setText(null);
    }
    else
    {
      picture.setText("Image not found");
    }
  }

  /** Returns an ImageIcon, or null if the path was invalid. */
  protected static ImageIcon createImageIcon(String path)
  {
    java.net.URL imgURL = ComboBoxDemo.class.getResource(path);
    if(imgURL != null)
    {
      return new ImageIcon(imgURL);
    }
    else
    {
      System.err.println("Couldn't find file: " + path);
      return null;
    }
  }

  /**
   * Create the GUI and show it. For thread safety, this method should be
   * invoked from the event-dispatching thread.
   */
  private static void createAndShowGUI()
  {
    // Create and set up the window.
    JFrame frame = new JFrame("ComboBoxDemo");
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

    // Create and set up the content pane.
    JComponent newContentPane = new ComboBoxDemo();
    newContentPane.setOpaque(true); // content panes must be opaque
    frame.setContentPane(newContentPane);

    // Display the window.
    frame.pack();
    frame.setVisible(true);
  }

  public static void main(String[] args)
  {
    // Schedule a job for the event-dispatching thread:
    // creating and showing this application's GUI.
    javax.swing.SwingUtilities.invokeLater(new Runnable() {
      public void run()
      {
        createAndShowGUI();
      }
    });
  }
}
